1. Field of Invention
This invention relates to a cylinder, a load port using it and a production system using the load port, and in particular, to a load port which complies with the SEMI standard and is suitable for FOUPs (Front Opening Unified Pods) having a variety of latchkey receptacle shapes.
2. Description of the Related Art
Until now, open cassettes have been mainly used as a container which stores a plurality of semiconductor wafers. However, in order to reduce the production cost of high-performance semiconductor devices, the mini-environment systems have been advocated, which reduce the cost related to a clean room. In the mini-environment systems, the SMIF (Standard Mechanical Interface) system is widely used for 200 mm-wafers, and the FOUP (Front Opening Unified Pod) system is being examined to be used for 300 mm-wafers.
The FOUP system was advocated and provisionally standardized at SEMI (Semiconductor Equipment and Materials International) composed of semiconductor manufacturing equipment manufacturers and material manufacturers all over the world. Semiconductor device manufacturers are also preparing to construct the mass-production line with this system. The FOUP system was technically examined at the standard committee of SEMI and was provisionally standardized. Here, the SEMI standard E57-0299 strictly defines the accuracy of the load port mechanical interface method to open and close an FOUP door; on the other hand, it allows FOUP manufacturers more latitude in adopting mechanical interface of FOUP.
The FOUP system, for example, is described in detail in JP8-279546A. The structure and the opening and closing mechanism of FOUP are explained by referring to FIGS. 12 and 13. FIG. 12 is a perspective view of a load port carrying out the opening and closing of FOUP door. Here, load port 30 is composed of frame 31 having a opening, stage 32 which is enable to move in the frame direction and has three kinematic pins 34 on the surface, and port door 33 which is inserted into the opening from opposite direction to stage 32 and retracted from the opening. In port door 33, two registration pins 36 are mounted diagonally, and two latchkeys 35 that rotate between the vertical position (90-degree position) and the horizontal position (0-degree position) are installed. Additionally, holding pads 37 are installed surrounding respective registration pins 36 to fix FOUP door 52 to port door 33.
FOUP 50 is composed of FOUP box 51 and FOUP door 52, as is shown in FIG. 13. FOUP box 51 has a plurality of shelves to hold wafers 53 and handles 58 for carrying by hand. In FOUP door 52, latch holes 55 and registration holes 54 are formed at corresponding positions to latchkeys 35 and registration pins 36 of port door 33. Inside latch holes 55, a latchkey receptacle is installed to engage with latchkey 35. The locking and unlocking operation of latches 56 is carried out by turning the latchkey receptacles using the latchkeys.
It is stipulated in the SEMI standard that fixing and unfixing of FOUP door 52 to and from FOUP box 51 is made by turning the latchkey receptacles to the positions of the 90-degree and the 0-degree, respectively. However, there is no concrete stipulation on the fixing method of FOUP door, and therefore, FOUP manufacturers are allowed to adopt their own method. The opening and closing mechanism of FOUP door is described in, for example, U.S. Pat. No. 5,915,562.
One of the FOUP opening and closing operations will be explained below. An FOUP is placed on stage 32 having three kinematic pins 34 mounted thereon and is aligned with the aid of the kinematic pins. Then, stage 32 is moved forwards to insert registration pins 36 of the port door into registration holes 55 of FOUP 50, whereby the FOUP door is positioned against the port door. Further advance of the stage makes latchkeys 35 of the port door engage with latchkey receptacles through latch holes 55 of FOUP, and the FOUP door finally contacts with the port door. At this stage, the inside of holding pads 37 installed around the root of registration pins 36 are evacuated to fix the FOUP door to the port door.
Then, the FOUP door is detached from the FOUP box by turning latchkeys 90 degrees to the 0-degree position. The port door, holding the FOUP door, is moved backwards and then downwards. Thus, wafers can be taken out through the opening. Each wafer stored in the FOUP box is transferred by e.g. a scalar type robot disclosed in JP No.2749314 to a wafer process tool.
When the FOUP door is closed, the same operation is made in reverse order.
This FOUP system was established as a provisional specification of SEMI in 1996, and each company has developed and manufactured FOUPs and load ports on the basis of this standard. Various disadvantages about the FOUP system have been clarified with advancing the verification of operation.
As mentioned above, there is few stipulation on FOUP, in spite of strict stipulation on the load port: for example, the shape and size of latchkey are defined including their tolerance, but those of latchkey receptacle are not. Therefore, the following problems have arisen. According to the SEMI standard E62-0999, the tolerance on the rotation angle of latchkey is defined as xc2x11 degree at the 0-degree position and 90-degree position. However, since there is no stipulation on the size of the latchkey receptacle, latchkey receptacles may not rotate 90 degrees even if latchkeys rotate by 90 degrees, as shown in FIG. 8(A), in the case where the width W1 of latchkey receptacles 57 is to some extent larger than the width W2 of latchkey 35. That is, latchkey receptacles may not rotate to the 90-degree position, but to the (90xe2x88x92xcex8) degree position depending on the difference of (W1-W2), which results in failing to lock the latches. The latchkey receptacles happen not to be at the 90-degree position even though the latches have been locked. When this FOUP is transported to the load port of next process tool and the stage thereof is moved forwards to open the FOUP, the latchkeys may contact or collide with latchkey receptacles of the FOUP door. The contact or collision causes dust generation and contaminates the wafer transferring space. Furthermore, the repetition of the contact and collision may deform the latchkey receptacles and finally destroy the FOUP door. If the latchkey receptacle is deformed, they cannot rotate to the 0-degree position when latchkeys rotate to the 0-degree position. Thus, latchkey receptacles will stop at e.g., 5 degrees that is out of tolerance range of xc2x11 degree. As a result, the FOUP door cannot be detached from FOUP box, which is a severe disadvantage in the manufacturing process of semiconductor devices and the like.
Although each FOUP manufacturer has carried out various examinations in order to solve the above problems, the appropriate solution has not been obtained from the viewpoint of cost and reliability.
Then, the inventors have developed the load port which can make latchkey receptacles into the 90-degree position by rotating the latchkeys more than 90 degrees when to lock the latches (Japanese Patent Application 2000-59654). This makes possible the stable latching operation. However, it was found in the case of the production system including a conventional load port that the latchkey receptacle angle often greatly deviated from 90 degrees depending on the type of FOUP and that the latchkey contacted the latchkey receptacle to damage. This will be explained using FIG. 14.
FIG. 14 is a graphical representation showing the latchkey receptacle angles for two types of FOUP after latches are locked. Here, the production system is composed of conventional load ports (C and G) and new type load ports (A, B, D, E, F, and H). The latchkey receptacles were made at almost 90 degrees for any FOUP when the latches were locked using the new type load port (A, B, D, E, F, and H), but they happened to be at about 86 degrees when the conventional load port (C and G) is used. When this FOUP is transported to the next load port, the latchkeys contacted the latchkey receptacles and caused the damage in the latchkey receptacles even if the next load port was a new type (D or H).
Under such circumstances, the object of the present invention is to provide the load port which makes it possible for FOUP whose latchkey receptacles are not at the 90-degree position to certainly insert latchkeys into latchkey receptacles without causing the damage in the latchkey receptacles when the stage moves forwards to open FOUP.
The further object of this invention is to provide a smaller-sized cylinder suitably used for the load port. Another object of this invention is to provide a production system which enables the mass-production with high reliability of semiconductor integrated circuits.
In order to solve the above-mentioned problems, the inventors examined the insertion method of a latchkey to a latchkey receptacle and the latching mechanism in detail by using a cylinder as a driver of latchkey. It has been found as a result of these examinations that by making the latchkeys freely rotatable when the latchkeys are being inserted into the latchkey receptacles, the latchkeys are rotated following the latchkey receptacle angle of (90xe2x88x92xcex1) to be smoothly inserted into the latchkey receptacles as shown in FIG. 8(C). Thus, the damage of the latchkey receptacles and the dust generation can be avoided. Here, the behavior that the latchkey begins to rotate when it contacts the latchkey receptacle to adapt to (or compensate) the angle deviation (xcex1) and is smoothly inserted into the latchkey receptacle is shown in plan and sectional views of FIGS. 9(B)-9(D). FIG. 9(A) is a schematic diagram showing the configuration of the latchkey and the latchkey receptacle.
In addition, when the FOUP door is closed by locking latches, as shown in FIG. 8(B), latchkeys are rotated more than 90 degrees (90+xcex8) and thereafter are returned to the 90-degree position so that latchkey receptacles may be at the 90-degree position. By this method, latches can be certainly locked for any FOUP and latchkey receptacles are returned to the 90-degree position. Thus, the stable latching operation is maintained even for the production system, which includes the conventional load ports.
This method requires a cylinder whose piston rod stops accurately at four different positions corresponding to four latchkey angles. A multiposition cylinder which makes it possible to stop the piston rod at many positions is disclosed in e.g., JP8-82305A. However, this cylinder requires four actuators for driving stoppers to stop the piston rod and therefore the size of the whole cylinder becomes too large to be installed in the port door of SEMI standard. Moreover, although it is also possible to construct a four-position cylinder by connecting the conventional cylinders, the size of the whole cylinder similarly becomes very large.
Therefore, the present inventors further studied the cylinder structure which can be miniaturized based on these knowledge, and have finally accomplished cylinders of this invention.
A cylinder of this invention in which a piston rod performs linear motion with the pressure of fluid applied to a piston through two fluid ports, is constructed so that by one stop pin, the end portion of said piston rod stops at the first position which is one end of the maximum actuation range thereof, the second position which is the other ends of the maximum actuation range, the third position which is located between the first position and the second position and nearer said second position, and the fourth position which is located between the first position and the third position and nearer the third position.
The cylinder of this invention is further characterized in that the end portion of the said piston rod can move freely between the third position and the fourth position. Here, the stop pin may be driven by, for example, fluid pressure, spring force and electromagnetic force or the like.
The cylinder of this invention which moves the piston rod among four positions specifically comprises: a spring receiving member placed coaxially with said piston rod in a piston room of a cylinder tube so that the movement of said spring receiving member is limited by one end of said piston room; a first spring member to separate said spring receiving member from said piston; a stopper formed on said piston rod to limit said spring receiving member from moving in the opposite direction to said piston; a hollow formed on the periphery of said piston rod at farther position from said piston than said stopper; and a stop pin installed in said cylinder tube to be pressed in the direction of said hollow by a second spring member to engage with said hollow, the movable length of said piston rod while said stop pin is engaged with said hollow being larger than movable distance of said spring receiving member from said piston.
Here, for instance, the four positions of the piston rod are determined by the first position where said piston comes in contact with the first end of said piston room which is opposite side of said stop pin, the second position where said spring receiving member comes in contact with the second end of said piston room and the distance between said piston and said spring receiving member becomes minimum or where said stop pin comes in contact with the piston side end of said hollow, the third position where said spring receiving member comes in contact with both said second end of said piston room and said stopper, and the fourth position where said stop pin comes in contact with the other end of said hollow.
With such structures, the four poisons of the piston rod can precisely be determined and the transfer among these positions can also be stably carried out. In addition, as compared with the tandem type cylinder made by connecting two cylinders and the cylinder disclosed in JP8-82305A, the number of component parts and accessories can be remarkably reduced, meaning that this invention has an advantage in cost reduction. As a result, it becomes possible to construct a compact, low-price, four-position type cylinder having high reliability in operation.
A load port of the present invention is composed of: a frame having an opening; a stage holding a substrate container having a front door to seal inside airtight using a latch; and a port door having a latchkey and a cylinder to rotate said latchkey, and which locks and unlocks said latch by rotating said latchkey in the state where said front door is in full contact with said port door and said latchkey is engaged with a latchkey receptacle of said front door, wherein said latchkey is rotated to adapt to the angle deviation of latchkey receptacle as said front door is brought in contact with said port door so that said latchkey is inserted to and engaged with said latchkey receptacle.
Here, as a cylinder for driving a latchkey, the cylinder of this invention mentioned above which send the piston rod to four different positions is preferably adopted.
By using the load port having the construction mentioned above, it is possible to avoid the imperfect latching operation, the damage during latchkey insertion and the dust generation. That is, the front door of FOUP can be opened without any trouble even for FOUP whose latchkey receptacles are not at 90-degree position, since the latchkeys are smoothly inserted into the latchkey receptacles following their angles, and the latchkey receptacles are returned to the 90-degree position after the front door is closed. Therefore, the collision between the latchkey and the latchkey receptacle, the damage and the particle generation can be avoided even in the production system which includes the conventional load ports.
As shown in FIG. 14, the angle (90xe2x88x92xcex1) of the latchkey receptacles is generally between 86-92 degrees after the latch is locked. Therefore, the values of xcex8 and xcex2 were set to satisfy the equations of (90+xcex8)=90xe2x88x9294xc2x0 and (90xe2x88x92xcex2)=85xe2x88x9290xc2x0 to carry out the stable latching operation even for the production system, which includes the conventional load ports.
The four positions of the cylinder are determined, corresponding to these angles. That is, the first, second, third and fourth positions are respectively determined to correspond to the 0 degree (horizontal position), the angle larger than 90 degree (90+xcex8), 90 degree (vertical position) and the angle less than 90 degree (90xe2x88x92xcex2), which enables reliable latching operation.
This structure makes possible more reliable latching operation. Additionally, this structure is compact enough to be easily installed in the port door which meets the SEMI standard.
In this invention, the load port is preferably constructed so that two latchkeys are connected and simultaneously turned by single cylinder. This reduces the number of cylinders, valves and the like and therefore reduce the cost of load port.
And a production system of this invention is characterized in that the load port of this invention is used.